MJML Email Preview — Test Gmail, Outlook & Mobile Before Sending

Paste your MJML above and MailViewr compiles it to HTML right in your browser, then renders it across Gmail, Outlook, Apple Mail and mobile — including dark mode. 5 free previews, no signup.

Open the full-screen MJML editor

Everything you need to preview MJML

The official MJML compiler turns MJML into HTML. MailViewr does that and everything after — previewing, testing and QA across real email clients, all in one place.

Compile MJML to HTML

Browser-side compilation with the official MJML engine — no install, 5 free previews before signup.

Gmail preview

See your compiled MJML in Gmail web, iOS and Android.

Outlook preview

Catch Word-engine quirks before you send.

Apple Mail & mobile

Preview macOS, iOS and mobile clients side by side.

Dark mode preview

Test how your MJML renders in Gmail and Apple Mail dark mode.

Pre-Send QA report

Run structural checks and a SpamAssassin score on the compiled HTML.

Download HTML

Export the generated, email-ready HTML for any ESP.

CSS compatibility

Get per-client compatibility scoring on the output.

Supported MJML components

MailViewr previews emails built from the full MJML component set, including:

<mj-section><mj-column><mj-button><mj-image><mj-text><mj-social><mj-table><mj-navbar><mj-carousel><mj-wrapper><mj-group><mj-divider><mj-spacer><mj-hero><mj-accordion><mj-raw>

From MJML to a rendered email

Write concise MJML, compile to responsive HTML, and preview how it actually renders.

Your MJML

<mjml>
  <mj-body>
    <mj-section>
      <mj-column>
        <mj-text font-size="20px">Welcome aboard 🎉</mj-text>
        <mj-button href="https://example.com">Get started</mj-button>
      </mj-column>
    </mj-section>
  </mj-body>
</mjml>

What you get

Responsive, Outlook-safe HTML
  → previewed in Gmail, Outlook,
    Apple Mail & mobile
  → dark mode tested
  → QA report + downloadable HTML

MJML vs HTML

MJML compiles to HTML, so you get responsive, Outlook-safe markup with far less code. MailViewr supports both — paste either and preview across clients.

Aspect	MJML	Hand-written HTML
Responsiveness	Automatic, mobile-first	Manual media queries
Outlook support	Generated table markup, Word-safe	You write the VML/conditionals
Maintainability	Concise, component-based	Verbose, nested tables
Development speed	Fast — fewer lines	Slower — more boilerplate
Output	Compiles to HTML	Already HTML

MJML preview FAQ

Can I preview MJML emails online?

Yes. Paste your MJML into MailViewr and it compiles to HTML in your browser, then renders across Gmail, Outlook, Apple Mail, Yahoo and mobile devices — including dark mode — so you can see exactly how it looks before sending.

Does MailViewr convert MJML to HTML?

It does. MailViewr compiles MJML to email-ready HTML in the browser using the official MJML engine. You can preview the result, run a QA report, and download the generated HTML for any ESP.

Can I test MJML in Outlook?

Yes. After compiling your MJML, MailViewr previews the HTML in Outlook (desktop and mobile) alongside Gmail and Apple Mail, so you can catch Word-engine rendering issues before you send.

Is the MJML compiler free?

Completely free, with no install required. Open the editor, paste your MJML, and preview instantly — 5 free previews before signup.

Is my MJML uploaded or stored?

No. MJML is compiled entirely in your browser. Your source is never uploaded to a server just to preview it.

MJML vs HTML — which should I use?

MJML is faster to write and produces responsive, Outlook-safe HTML automatically, which is ideal for new builds. Hand-written HTML gives you the most control. MailViewr supports both — paste either and preview across clients.